It is very important in the production of food products to retain good flavors of just-made foods or drinks until they are eaten or drunk, and develop the good flavors when necessary.
However, in the actual food industries, the flavors inherent in such products as seasonings, processed foods or the like may be weakened or lost by such operations as concentration, drying or the like during the production process of the products. Meanwhile, flavors unfavorable to commercial products may develop during the production process or distribution channel. Under the circumstances, a technology for enhancing good flavors of food or drink products and developing the good flavors stably over a long time period has been strongly desired.
Meanwhile, a number of studies have been so far made on the technology for controlling the retention and development of aromas (“Latest Technology for Food Flavors”, issued by Kougyo Gijyutsukai in 1988). For example, encapsulation of aromas in microcapsules, confinement of aromas in matrices, inclusion of aromas by cyclodextrin or the like, action of enzymes on volatile aroma constituent precursors such as glycosides are known.
However, there are problems, e.g., in a method of physically retaining aromas, it is difficult to control its amount of development at will, whereas in a method using glycosides, it has such problems that the target compounds are limited only to alcohols and that enzymes used are deactivated in a system heated for using the enzymes.
Further, as to processed foods, the flavors inherent in the products may be weakened or lost by such operations as concentration, drying or the like during the production process of the products.
Meanwhile, sulfur-containing compounds which are aroma substances generally has a low aroma threshold and often play an important role in aroma characteristics for perfume cosmetics, food products and the like. For example, it is known that fran-derivative thiol compounds (such as 2-Furylmethanethiol (FMT) and 2-Methyl-3-furanthiol (MFT) and the like) greatly contribute to the aromatizing of foods including coffees and livestock meats (“Sulfur Compounds in Foods”, ACS Symposium Series 564, American Chemical Society (1994)). However, since these thiol compounds have a low threshold, it is difficult to retain the development amount of their aroma within a proper range and to retain their aroma concentration within a predetermined range over a long time period. Therefore, a method for retaining or developing the aroma effectively has been expected to be developed.
It is very important, as has been described, in the production of food products to retain good flavors of just-made foods or drinks until they are eaten or drunk and develop the good flavors when necessary.
However, in the actual food industries, flavors are gradually volatilized and weakened or lost, or degraded or turned into unpleasant odors during each step of production, distribution, storage, and the like. Under these circumstances, a technology for enhancing good flavors of food or drink products and developing the good flavors stably over a long time period has been strongly desired.
Meanwhile, as has been also described, a number of studies have been so far made on the technology for controlling the retention and development of aromas (“Latest Technology for Food Flavors”, issued by Kougyo Gijyutsukai in 1988). For example, encapsulation of aromas in microcapsules, confinement of aromas in matrices, inclusion of aromas by cyclodextrin or the like, action of enzymes on volatile aroma constituent precursors such as glycosides are known.
Further, as a method for preventing the volatilization of aroma components, there have been proposed, e.g., a method in which an aroma material is dissolved in a solvent material which can dissolve the aroma component of the aroma material and which has a higher boiling point than the sublimation and/or volatilization temperature of the aroma component, and then the resulting mixture is mixed into foods or perfume cosmetics (Japanese Patent Application Laid-Open No. 50084/1999), a method of blending polylysine or a salt thereof as active ingredients (Japanese Patent Application Laid-Open No. 30712/1994), and a method of adding a whey protein or a derivative thereof to foods or drinks; and for the purpose of enhanced storage stability of aromas, there have been proposed a method of sealing or confining an aroma component within carbohydrate(s), as exemplified by a sorbitol-encapsulated flavor obtained by sealing or confining a flavor within a molten mixture of sorbitol, mannitol and saccharine (Japanese Patent Application Laid-Open No. 71866/1983), a composite flavor having a flavor contained in xylitol (Japanese Patent Application Laid-Open No. 76062/1983), and the like.
As for a method for suppressing unpleasant odors of foods or drinks, there have been practiced, as measures for preventing the deterioration of aromas by oxygen, the development of a container or bag made of a synthetic resin having a reduced oxygen permeability, the introduction of a food production process comprising deoxygenation operations, the addition of antioxidants, and the like. As measures for preventing the deterioration of aromas by light, there have been proposed a milk-containing acidic drink to which rutin, morin or quercetin has been added for the purposes of preventing the occurrence of substances causing unpleasant odors and/or tastes and improving preservability (Japanese Patent Publication No. 21450/1992); a method of preventing the deterioration of flavors by sunshine by using chlorogenic acid, caffeic acid or ferulic acid which are derived from the extracts from raw coffee beans, and vitamin C, rutin or quercetin in combination (Japanese Patent Application Laid-Open No. 27374/1992); and a method of preventing the deterioration of a natural aroma material by adding chlorogenic acid derived from coffee beans to a aroma composition derived from a natural material (Japanese Patent Application Laid-Open No. 345693/1992). Further, as measures for suppressing the deterioration of flavors by light, heat or oxygen, a method wherein a specific flavone derivative is used (Japanese Patent Application Laid-Open No. 169148/1999) has been proposed.
Meanwhile, it has heretofore been well known that a variety of thiols are widely distributed as aroma components in a variety of food products. The thiols include those which are contained in naturally occurring materials such as vegetable essential oil and the like as well as those which are produced secondarily by heat treatment, enzyme reaction or the like at the time of processing. These have the problem that the aromas inherent in such thiols are lost by heat treatment at the time of food processing such as sterilization treatment and the like or by long-time preservation, and it is thought that the problem is caused by the decomposition, deterioration or volatilization of the thiols by heat. In Japanese Patent Application Laid-Open No. 281697/2000 disclosed is a method in which when a thiol compound exhibiting an aroma is used in the form of a glycoside, the stability of the thiol compound against the heat or the like applied during the production process of food products is increased, while the aroma inherent in the thiol is also exhibited as the glycoside is gradually decomposed due to the influences of heat and/or pH, whereby the aroma can be prolonged although the thiol compound is used in low concentrations due to a low threshold. However, the method does not have the function of developing aroma at the time of eating foods and is therefore different from the present invention described below in greater detail.
The background art concerning frozen foods is as follows:
Conventionally, when a component having a strong aroma volatility is to be incorporated into frozen foods, an essential oil-like component is added as it is or the component in the form of a powder obtained by causing dextrin or the like to adsorb the component and powdering the resulting product, is added. According to this method, however, it is difficult to cause a sufficient amount of the component to remain in an end product since most of the component is volatilized under severe heating conditions such as frying or the like. Further, since the volatilization of the component added proceeds gradually during frozen preservation, measures such as sealing with the use of a gas-impermeable packaging materials, or the like, must be taken.
Further, there has been proposed a frozen food which contains an oil-like aroma volatile component encapsuled in capsules whereby the aroma volatile component remains in an sufficient amount in the end product even after the product has undergone a heating operation (Japanese Patent Application Laid-Open No. 014332/2000), and there has been also proposed a composition containing an amino acid, reducing sugar, protein and water as a topping composition for a microwave oven which topping composition is capable of giving favorable browning and/or roasted savor to foods by microwave cooking (Japanese Patent Application Laid-Open No. 103790/1999).
Further, the background art concerning retort foods is as follows:
As is well known, retort foods include so-called “retort pouch foods” (in the narrow sense) produced by filling with food material, a bag-shaped container (pouch) made of a light-shielding plastic film obtained by laminating an aluminum foil or a transparent plastic film having a low oxygen permeability, sealing the opening of the container by heat sealing and subjecting the container to commercial heat sterilization at temperatures higher than 100° C. by using a pressurized sterilizer (retort) as well as canned foods and bottled foods (in the broad sense). Since the retort foods can be preserved over a long time period at room temperature, they are widely used due to convenience thereof.
However, since retort foods are produced by being subjected to heat treatment at high temperatures (retort treatment), a so-called “retort odor” which is an unpleasant odor may be produced. This has been considered unfavorable from the viewpoint of product quality.
Substances causing the unpleasant odor (to be sometimes referred to as “retort odor” hereinafter) are not yet identified.
To alleviate the retort odor, the easing of conditions for heat sterilization and the like have heretofore been studied. However, in order to distribute retort foods at ordinary temperature, they must be sterilized at high temperatures to some extent, and the easing of the conditions for heat sterilization is limited as an operation for preventing the deterioration of flavors.
Further, there have been proposed a method in which a gas-impermeable package is used as the package for retort foods (Japanese Patent Application Laid-Open No. 29845/1992) and a method in which the inside of the package is substituted with a nitrogen gas at the time of sterilizing the retort food (Japanese Patent Application Laid-Open No. 254167/1986). In addition, a method in which cyclodextrin is added at the time of producing retort foods (Japanese Patent Application Laid-Open No. 75366/1985), a method in which sucrose fatty acid ester is added at the time of producing retort foods (Japanese Patent Application Laid-Open No. 17407/1982) have also been considered.
However, the improvement in the package and the substitution with nitrogen increase costs, since the existing packaging materials and filling equipment must be altered accordingly. Meanwhile, satisfactory results have not been obtained by the method using cyclodextrin or sucrose fatty acid ester.
Thus, the development of a simple and effective method for suppressing or masking the retort odor whereby the flavor of retort foods is improved, has been desired.
Furthermore, the background art concerning soybean-incorporated or -utilized food products is as follows:
Soybean protein may be mentioned as a typical example of soybean-incorporated or -utilized food products. The soybean protein which is a vegetable protein, is used not only as a major edible protein source but also in a variety of food processings by taking advantage of its characteristics and is expected to be used more and more in the future along with increasing consciousness in health.
However, although soybean protein is excellent from the viewpoint of its nutritive value and functionalities such as emulsifying property and the like, it is limited in many cases when it is used as an ingredient or raw material of food, since it has a unique taste, smell, color and the like. Further, it is known that the unique taste and smell are greatly attributable to the lipid moiety remaining in the soybean protein. In other words, unsaturated fatty acids such as linoleic acid, linolenic acid and the like cause oxidation due to enzymatic or non-enzymatic factors and are converted into carbonyl compounds or the like typified by aldehydes such as hexanol, and the like, and it is said that these substances are attributable to the taste and smell peculiar to defatted soy milk, isolated soybean protein, or the like.
Therefore, for removing or alleviating the unpleasant odor peculiar to soybean protein, a number of studies have heretofore been made. There are known, for example, methods such as enzyme treatment, microorganism treatment, activated carbon treatment,. thermo-vacuum treatment and the like (Wolf, W. J.: J.Agric.Food Chem., 23, 136(1975), Ryuzo Sasaki, Hideo Chiba; Chemistry and organism, 21, 536(1983), Warner, K., Mounts, T. L., Rackis, J. J. and Wolf, W. J.; Cereal Chem., 60, 102(1982) and so on). Further, as a simple method, a method in which a variety of masking agents are added has also been studied.
Further, a method in which a solution containing soybean protein is brought into contact with a weak-basic anion-exchange resin, an amphoteric ion-exchange resin or a functional group-free synthetic adsorption resin to remove the “soybean odor” peculiar. to soybeans which is called “bean-like odor” or “weed-like odor”, has also been studied (Japanese Patent Application Laid-Open No. 276955/1994).
However, the above methods such as enzyme treatment, microorganism treatment, activated carbon treatment, thermo-vacuum treatment, ion-exchange resin treatment and the like have not yet succeeded in removing the unpleasant odor, that is, soybean smell, completely. In addition, these treatments make the process complicated and increase costs, and are therefore accompanied with some problems to be solved with regard to actual applications. Further, the above-described method of adding masking agents exhibits some effects, but it is basically not for removing the soybean smell. Therefore, the method has the problem that it can not be applied when soybean protein is used as the main ingredient in high concentrations and its amount to be used is restricted.